The present invention relates to a crystalline mixture solid composition which comprises
xcex1-D-glucopyranosyl-1,1-mannitol and
xcex1-D-glucopyranosyl-1,6-sorbitol and may further comprise
xcex1-D-glucopyranosyl-1,1-sorbitol in a certain case and to a process for the preparation thereof.
Hydrogenated palatinose (hydrogenated isomaltulose) has been known as one of low-calorie sweeteners which do not cause a carious tooth. The hydrogenated palatinose is a mixture of two sugar alcohols, that is, an almost equimolar mixture of xcex1-D-glucopyranosyl-1,1-mannitol (to be abbreviated as GPM hereinafter) and its isomer xcex1-D-glucopyranosyl-1,6-sorbitol (to be abbreviated as GPS-6 hereinafter), which can be obtained by forming palatinose (isomaltulose) from cane sugar by means of a transferase and then hydrogenating the palatinose.
The hydrogenated palatinose is known as an extremely useful sweetener which exhibits an excellent sweet taste like cane sugar, has low hygroscopicity, heat resistance, acid resistance, alkali resistance, excellent processability such as tablettability and granulability, and physiological properties such as low calorie, noncariogenic properties and insulin non-irritating properties.
As the method of crystallizing the hydrogenated palatinose, H. Schiweck""s report (Alimenta. 19,5-16, 1980) discloses a vacuum crystalizar process. However, this process is very complicated and repeats the steps of evaporation, aging and centrifugation, thereby consuming a huge amount of energy and boosting product costs.
JP-A 60-181094 (the term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d) discloses a process for crystallizing an aqueous solution of hydrogenated palatinose having a solid content of about 80% in a vacuum crystallization apparatus. However, since this process requires a special apparatus such as a vacuum crystallization apparatus and employs a batch system, it is not practical due to its low production efficiency.
JP-A 62-148496 discloses a process for crystallizing hydrogenated palatinose in accordance with a kneading method using seed crystals. This process is used to crystallize mainly a GPM component out of hydrogenated palatinose components. That is, the water content of the hydrogenated palatinose is adjusted to a range of more than 5% and 20% or less, the liquid temperature is maintained at a range of 50 to 90xc2x0 C. according to the content of water, seed crystals are added and mixed, and the mixed product is solidified by cooling the temperature at around room temperature, dried and ground to obtain crystallized hydrogenated palatinose powders. However, this process has a problem with processing (such as grindability) as the kneaded product obtained by this process has high stickiness and also a problem with distribution (such as caking and the propagation of microorganisms) as cooling and drying take long time.
It is also known that when a transferase is caused to act on cane sugar, trehalulose (xcex1-D-glucopyranosyl-1,1-fructose) is formed in addition to isomaltulose. Generally speaking, when hydrogenated palatinose is produced, after only palatinose is obtained by crystallization separation, the residual mixture containing trehalulose is discarded or disposed at a low cost. It is known that trehalulose is converted into GPM and xcex1-D-glucopyranosyl-1,1-sorbitol (to be abbreviated as GPS-1) by hydrogenation. That is, when a transferase is caused to act on cane sugar as a raw material and the obtained mixture is hydrogenated, a mixture of GPM, GPS-6 and GPS-1 can be obtained. To obtain such a mixture, a process is known as disclosed in JP-A 7-51079. This process comprises the first step of carrying out the conversion reaction of cane sugar, the second step of removing unreacted cane sugar and the third step of carrying out a hydrogenation reaction in the presence of a catalyst. As for solidification, the above publication discloses a fine particulate product obtained by vaporizing water for solidification and grinding. However, the product is an amorphous and glass-like solid, has high hygroscopicity, and is difficult to handle and easily worn by abrasion during circulation.
In object of the present invention to provide a crystalline mixture solid composition which has almost no hygroscopicity, is easy to handle and dissolve, and hardly worn by abrasion, comprises GPM, GPS-6 and GPS-1.
It is another object of the present invention to provide a composition which comprises GPM and GPS-6 and may further comprise GPS-1 in a certain case and has a specific surface area of 0.07 to 0.1 m2/g.
It is still another object of the present invention to provide a power-saving and labor-saving process for producing the above composition of the present invention in an extremely short period of time with a small-scale apparatus.
Other objects and advantages of the present invention will become apparent from the following description.
According to the present invention, firstly, the above objects and advantages of the present invention are attained by a crystalline mixture solid composition which comprises 20 to 75 wt % of xcex1-D-glucopyranosyl-1,1-mannitol, 23 to 70 wt % of xcex1-D-glucopyranosyl-1,6-sorbitol and 2 to 25 wt % of xcex1-D-glucopyranosyl-1,1-sorbitol (above weight percentages are based on the total weight of
xcex1-D-glucopyranosyl-1,1-mannitol,
xcex1-D-glucopyranosyl-1,6-sorbitol and
xcex1-D-glucopyranosyl-1,1-sorbitol).
According to the present invention, secondly, the above objects and advantages of the present invention are attained by a composition which comprises 20 to 75 wt % of
xcex1-D-glucopyranosyl-1,1-mannitol, 23 to 70 wt % of
xcex1-D-glucopyranosyl-1,6-sorbitol and 2 to 25 wt % of
xcex1-D-glucopyranosyl-1,1-sorbitol and has a specific surface area of 0.07 to 0.1 m2/g.
According to the present invention, thirdly, the above objects and advantages of the present invention are attained by a composition which comprises 30 to 75 wt % of
xcex1-D-glucopyranosyl-1,1-mannitol and 25 to 70 wt % of
xcex1-D-glucopyranosyl-1,6-sorbitol and has a specific surface area of 0.07 to 0.1 m2/g.
Further, according to the present invention, fourthly, the above objects and advantages of the present invention are attained by a process for producing the above composition of the present invention, the process comprising the steps of:
(1) continuously supplying a raw material, which is obtained by optionally removing trehalulose from a mixture of isomaltulose and trehalulose produced from cane sugar through an isomerization reaction according to circumstances and hydrogenation into a kneader having a thin and long cooling zone together with seed crystals; and
(2) discharging the reaction product from an outlet continuously.
The present invention is described in detail hereinbelow.
A description is first given of the process of the present invention.
In the process of the present invention, the crystalline mixture solid composition of the present invention is produced from a raw material obtained by hydrogenating a mixture containing isomaltulose and trehalulose produced from cane sugar through an isomerization reaction. Before hydrogenation, trehalulose may be removed. The crystalline mixture solid composition of the present invention is produced by injecting the raw material into the kneader having a thin and long cooling zone together with seed crystals.
As for the preferred ratio of isomaltulose and trehalulose before hydrogenation, the amount of isomaltulose is 5 to 100% and that of trehalulose is 0 to 95%.
The crystalline mixture solid composition of the present invention can be produced by hydrogenating a mixture containing isomaltulose and trehalulose which is produced from cane sugar through an isomerization reaction or a mixture from which trehalulose has been removed without separating impurities. After hydrogenation, if necessary crystallization or the like is carried out as required to change the ratio of the three components.
The transferase used in the isomerization may be a culture of bacteria which is generally used for the production of isomaltulose, enzyme extracted from the bacteria or immobilized product thereof. The bacteria may be the one belongs to the genuses of Protaminobacter, Serratia, Erwinia, Klebsierra, Pseudomonas, Agrobacterium and Leuconostoc.
The water content of a mixed solution which contains GPM and GPS-6 and may contain GPS-1 in a certain case as a raw material may be adjusted to a level equivalent to the water of crystallization of GPM, preferably 2 to 10 wt %, more preferably 5 to 8 wt %.
The temperature of the raw material to be supplied into the kneader may be generally a temperature at which the seed crystals do not dissolve, preferably 70 to 140xc2x0 C., more preferably 90 to 130xc2x0 C. in view of high fluidity for handling ease and manipulation ease for the formation of a magma.
The temperature of a cooling portion for forming a magma may be adjusted to a temperature at which generated crystallization heat can be removed, preferably 100xc2x0 C. or less, more preferably 70xc2x0 C. or less.
The feed rate of the raw material which differs according to the type and capacity of the kneader in use is approximately 2 to 50 kg/hr when the KRC kneader (2S) of Kurimoto Ltd. is used.
Any seed crystals may be added if the mixed solution which contains GPM and GPS-6 and may contain GPS-1 in a certain case crystallizes within the kneader. For example, crystal powders having almost the same GPM/GPS-6/GPS-1 composition as the mixed solution as the raw material or recycled crystal powders produced by the present invention may be used. The seed crystals are preferably added at a rate of 0.1 to 25 kg/hr. The amount of the seed crystals is not particularly limited but preferably 2 to 50 wt %, more preferably 5 to 40 wt % based on the raw material in view of crystallization speed and costs.
Any kneader can be used in the present invention if it is of a closed type, can knead and cool at the same time, and can continuously extrude the product from an outlet after kneading and cooing in the presence of the seed crystals. For example, an extruder, continuous kneader, mixtron, kneadex or the like is used. Out of these, an extruder is preferred. Examples of the extruder include KRC kneader (of Kurimoto Ltd.), double-screw extruder for foods (of Nippon Steel Co., Ltd.) and double-screw cooking extruder (of W and P Co. Ltd. of Germany).
To discharge a magma from the kneader, the shape of the magma can be optionally selected from noodle-like, ribbon-like, bar-like and plate-like shape sand the like. In consideration of the subsequent cooling and grinding steps, the magma is preferably discharged in a noodle-like or ribbon-like shape. A porous plate provided at the outlet preferably has a pore diameter of 2 to 5 mm and a porosity of 10 to 40%.
Although the cooling method is not particularly limited, one in which magma discharged from the kneader is directly exposed to cool air, one in which magma is left at room temperature, and one in which magma is cooled to room temperature with cool air on a metal net belt may be employed.
The obtained crystalline mixture solid composition can be made powder by grinding or granule by granulation. The grinding and granulation methods are not particularly limited and commonly used grinders and granulators are used. If required, the obtained powder and granule may be dried by a generally used drying method.
According to the above process of the present invention, the crystalline mixture solid composition of the present invention is obtained. GPM and GPS-6 contained in the composition of the present invention are existent in a crystalline state at normal temperature whereas GPS-1 is amorphous at normal temperature. Therefore, the composition of the present invention apparently shows a crystalline state but when it contains GPS-1 or the like, it is expressed in view of the above fact that the composition is in a crystalline mixture solid state.
That is, the composition of the present invention is a crystalline mixture solid composition when it comprises 20 to 75 wt % of GPM, 23 to 70 wt % of GPS-6 and 2 to 25 wt % of GPS-1. Preferably, the amount of GPM is 29.5 to 75 wt % and that of GPS-6 is 24.5 to 70 wt %. More preferably, the amount of GPM is 29.5 to 65 wt % and that of GPS-6 is 30 to 65 wt %. The amount of GPS-1 is preferably 2.8 to 25 wt %, more preferably 2.8 to 15 wt %.
A composition which comprises 30 to 75 wt % of GPM and 25 to 70 wt % of GPS-6 and does not comprise GPS-1 and has a specific surface area of 0.07 to 0.1 m2/g is in a crystalline mixture solid state. The composition of the present invention comprises GPM and GPS-6 in a total amount of preferably 80 wt % or more, more preferably 90 wt % of more based on the solid content.
The composition of the present invention is preferably uniform in particle diameter so that particles having a particle diameter of 16 to 60 Tyler mesh should account for at least 70 wt % of the total.
The specific surface area of the composition of the present invention is preferably 0.07 to 0.1 m2/g, more preferably 0.075 to 0.09 m2/g.
The bulk density (apparent specific gravity) of the composition of the present invention is preferably 0.7 to 0.8 g/cc, more preferably 0.73 to 0.77 g/cc.
According to the above process, there can be obtained a high-quality powdery or granular crystalline mixture solid composition which does not require a drying step, is easy to handle and dissolve, and is hardly worn by abrasion.
The following examples and comparative examples are given to further illustrate the present invention.